Using a mixer, instead of a delay line, a technique invented by engineers at the University of Massachusetts (Amherst) could enable localization of transmitters to within inches while simultaneously permitting low data-rate communications.

"For many ultrawideband applications, such as monitoring patients in a hospital, you only need low data rates for telemetry like heart rates and respiration, but you need to know exactly where the patient is located," said electrical and computer engineering professor Dennis Goeckel. "For this application, ultrawideband communications is perfect."

One of the most promising approaches to UWB was to first send a nanosecond-sized reference pulse before each data pulse, giving the radio a time frame in which to search its spectrum for data bits. However, after nearly a decade of attempting to use delay lines to synchronize data collection, most research into that approach has come to a halt, according to Goeckel.

"You wouldn't' have thought a 20 nanosecond delay line was so difficult to build, but everybody has pretty much given up," said Goeckel. "So I presented this problem to my doctoral student, Qu Zhang, and together we came up with a fresh approach that works.

A prototype was developed within nine months, Goeckel added.

The new approach scraps the delay line idea for an mixer which is easy to build even for ultrashort pulses. A reference pulse is still sent, but is mixed together with the data bit and multiplied by a cosine. On the receiving end is another mixer with one input coming from the antenna and one from a sine-wave generator.

"All the receiver has to do is integrate the mixers' output to determine whether the transmitted bit was a one or a zero," said Goeckel. "We hope it will be adopted by the standards committee."

The research was funded through a $6 million UWB research grant from the University of Southern California, the University of California at Berkeley and University of Massachusetts along with a research grant from M/A-COM Inc.